Various technologies have recently been appearing for increasing the storage capacities of recording media such as disks. It is also demanded to record various kinds of data such as audio data and computer data for example without restrictions.
In the development of general-purpose media, it is important to take the compatibility and integrity with conventional recording/reproducing apparatuses for example into consideration. Moreover, it is desired that the media be used effectively for existing resources.
In what follows, one of Mini Disc systems in wide use today is taken for example.
As well known, a Mini Disc system records and reproduces audio data such as music by use of a Mini Disc (MD), which is a magneto-optical disk having the diameter of 64 mm. In this case, audio data are recorded as compressed to ⅕ to 1/10 in size on the basis of an ATRAC method, one disk being able to record about 80 to 160 minutes of music data for example.
Because Mini Discs for audio use are easily available on the user side, it is preferable to apply Mini Discs to general-purpose uses other than music, for example, the data storage media for computers.
However, the following problems are preventing this application from being realized.
First, the recording capacity of the Mini Disc is relatively small, namely, about 160 MB.
Next, for the usage of the Mini Disc as a wide-range data storage, it is also supposed to use the Mini Disc for music and video distribution. However, the Mini Disc has no area for recording copyright protection information such as media-unique IDs that are required for the storage of distributed data for example, thereby failing to answer copyright protection requirements.
In addition, because control methods (P-TOC, U-TOC) based on unique control area other than the audio data recording area are employed, it is difficult to apply the Mini Disc to general-purpose file system using such as a FAT system for example.
Further, if data other than audio data are recorded to tracks under U-TOC management, many audio devices (MD players) suffer abnormal sounds at playback.
Namely, use of the audio Mini Disc for a general-purpose storage media is hampered by the problems associated with storage size, control system, special information such as copyright protection, compatibility and integrity with existing models.
It should be note that, for the purpose of recording data other than audio data in Mini Disc systems, disk standards generally referred to as “MD-DATA” and “MD-CLIP” have already been developed.
However, the MD-DATA standard cannot satisfy the above-mentioned requirements because a dedicated disk other than the audio MD is used and this standard is applicable to only dedicated recording/reproducing apparatuses corresponding to this standard and the recording capacity is only about 140 MB.
The MD-CLIP standard allows the use of audio MDs and uses the inner periphery portion of each MD, which is out of U-TOC control, thereby making this standard compatible with existing audio devices; however, that the general-purpose data recording area is only about 2 MB makes this standard to be limited in use.